Selective reshaping of nanoparticles in three dimensional articles

ABSTRACT

The present invention relates to processes for selective reshaping of nanoparticles in three dimensional articles, three dimensional articles produced by such processes, and methods of using such three dimensional articles. As a result of the aforementioned process, such three dimensional articles can have selective tuning that arises, at least in part, from the reshaped nanoparticles found in such articles. Such tuning provides the aforementioned articles with superior performance that can be advantageous in the areas including such as optical filters, multi-functional composites and sensing elements.

RIGHTS OF THE GOVERNMENT

The invention described herein may be manufactured and used by or forthe Government of the United States for all governmental purposeswithout the payment of any royalty.

FIELD OF THE INVENTION

The present invention relates to processes for selective reshaping ofnanoparticles in three dimensional articles, three dimensional articlesproduced by such processes, and methods of using such three dimensionalarticles.

BACKGROUND OF THE INVENTION

Three dimensional articles comprising nanoparticles such as opticalfilters, multi-functional composites and sensing elements are producedby processes that typically require multiple feed stock additivemanufacturing or two dimensional patterning of nanoparticles and thenstacking of such dimensional patterns to form a three dimensionalarticle—this process is known by the skilled artisan as spatiallymultiplexing different plasmonic effects via by site specific assembly.Unfortunately, such processes can only produce a limited number ofspecific three dimensional articles as multiple feed stock additivemanufacturing is limited to a small number of feedstocks and thestacking required in the three dimensional process is limited in thenumber of structures that can be made due to the inherent limitations,such as process controls, associated with the stacking process.

Applicants recognized that the source of the aforementioned problems wasthe fact that current processes reshaped the nanoparticles in thefeedstock material rather than in the three dimensional article itself.By reshaping the nanoparticles in the three dimensional article itself,each nanoparticle can be selectively shaped as desired to yield a highlyselectively tuned three dimensional article. Such tuning can include,but is not limited to, selective electromagnetic radiation absorption.Thus, Applicants disclose a process of reshaping the nanoparticles inthe three dimensional article and selectively tuned three dimensionalarticles.

SUMMARY OF THE INVENTION

The present invention relates to processes for selective reshaping ofnanoparticles in three dimensional articles, three dimensional articlesproduced by such processes, and methods of using such three dimensionalarticles. As a result of the aforementioned process, such threedimensional articles can have selective tuning that arises, at least inpart, from the reshaped nanoparticles found in such articles. Suchtuning provides the aforementioned articles with superior performancethat can be advantageous in the areas including such as optical filters,multi-functional composites and sensing elements.

Additional objects, advantages, and novel features of the invention willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentinvention and, together with a general description of the inventiongiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the present invention.

FIG. 1 Optical patterning of AuNR-PVA plasmonic nanocomposite. Beamprofile of a Xenon Arc lamp showing spatial distribution of theirradiation power density

FIG. 2 Optical patterning of AuNR-PVA plasmonic nanocomposite.Corresponding temperature profile induced from irradiating a AuNR-PVAfilm (AR˜2.8, ca. 50 nM, 25 mM CTAB, 100 μm.)

FIG. 3 Optical patterning of AuNR-PVA plasmonic nanocomposite.

Resulting film showing the color gradient.

FIG. 4 Optical patterning of AuNR-PVA plasmonic nanocomposite. Color mapfor various combination of exposure time and irradiation power forAuNR-PVA film (AR˜2.8, ca. 50 nM, 25 mM CTAB, 100 μm) without a glasssubstrate. Each spot ca. 1 mm.

FIG. 5 Optical patterning of AuNR-PVA plasmonic nanocomposite. Examplebinary pattern formation (ca. 40 mW/cm², spot size 100 μm, irradiationtime 100 ms.)

FIG. 6 Optical patterning of AuNR-PVA plasmonic nanocomposite. Exampleof a multi-exposure image of reshaped AuNRs where irradiation timealternates between 100 ms and 500 ms.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the sequence of operations as disclosedherein, including, for example, specific dimensions, orientations,locations, and shapes of various illustrated components, will bedetermined in part by the particular intended application and useenvironment. Certain features of the illustrated embodiments have beenenlarged or distorted relative to others to facilitate visualization andclear understanding. In particular, thin features may be thickened, forexample, for clarity or illustration.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Unless specifically stated otherwise, as used herein, the terms “a”,“an” and “the” mean “at least one”.

As used herein, the terms “include”, “includes” and “including” aremeant to be non-limiting.

Unless otherwise noted, all component or composition levels are inreference to the active portion of that component or composition, andare exclusive of impurities, for example, residual solvents orby-products, which may be present in commercially available sources ofsuch components or compositions.

All percentages and ratios are calculated by weight unless otherwiseindicated. All percentages and ratios are calculated based on the totalcomposition unless otherwise indicated.

It should be understood that every maximum numerical limitation giventhroughout this specification includes every lower numerical limitation,as if such lower numerical limitations were expressly written herein.Every minimum numerical limitation given throughout this specificationwill include every higher numerical limitation, as if such highernumerical limitations were expressly written herein. Every numericalrange given throughout this specification will include every narrowernumerical range that falls within such broader numerical range, as ifsuch narrower numerical ranges were all expressly written herein.

As previously stated, spatially multiplexing different plasmonic effectswithin a three dimensional structure is challenging, requiringfabrication of each component followed by site specific assembly.Post-fabrication methods that locally reshape a stock plasmonic unitafford substantial efficiency in constructing such pixelated andvoxelated materials. However, available approaches require large energydensity, pulsed lasers, lengthy time, or excessive control of reactantsto be viable for solid-state patterning at high manufacturing rates orin low temperature matrices, such as polymers, paper and biomaterials.

To address the challenge of post-fabrication reshaping, Applicantsdisclose a process that combines features of photo-thermal processeswith photo-chemistry at the nanoparticle surface using constraintsimposed by the matrix to provide isovolumetric control. Broadbandnon-coherent light sources, rather than pulsed lasers, are used toprovide photo-thermal heating to drive localized redox processes.Surprisingly, the nanoparticle volume and its single crystallinity areretained, and complete reshaping with light occurs 100× faster thancomparable thermal anneals (10 sec-100 sec v. hours to days). Finally,the process's dependency on optical power and reactant concentrationprovide approaches to spatially control the rate while preservingparticle alignment, enabling multi-exposure and multi-color patterning.Applicants' low energy, optically driven processes all cost-effective,rapid manufacture of materials with pixilated, voxelated or gradientplasmonic properties such as opto-electronics, colorimetric sensors,polarization sensitive filters, and imaging taggants.

Three Dimensional Articles

For purposes of this specification, headings are not consideredparagraphs and thus this paragraph is Paragraph 0023 of the presentspecification. The individual number of each paragraph above and belowthis paragraph can be determined by reference to this paragraph'snumber. In this paragraph 0023, Applicants disclose a three dimensionalarticle comprising:

-   -   a) a matrix material; preferably said matrix comprises a polymer        that serves as a reductant;    -   b) a population of nanoparticles;    -   c) an optional oxidant; and    -   d) an optional reductant        said population of nanoparticles being dispersed in said matrix        material to provide a morphology gradient greater than 0.03        nm/μm, preferably greater than 0.03 nm/μm to about 3 nm/μm more        preferably greater than 1 nm/μm to about 3 nm/μm, most        preferably greater than 2 nm/μm to about 3 nm/μm.

Applicants disclose a three dimensional article according to Paragraph0023, wherein said population of nanoparticles are plasmonic, preferablysaid population of nanoparticles comprises nanoparticles that comprise amaterial selected from the group consisting of gold, silver copper,platinum palladium, aluminum and mixtures thereof, more preferably saidpopulation of nanoparticles comprises nanoparticles that comprise amaterial selected from the group consisting of gold, silver and mixturesthereof.

Applicants disclose a three dimensional article according to Paragraphs0023 through 0024, said three dimensional article comprising, based ontotal three dimensional article weight, from about 0.001% to about 0.2%,more preferably, from about 0.01% to about 0.2%, most preferably fromabout 0.1% to about 0.2% of said nanoparticles.

Applicants disclose a three dimensional article according to Paragraphs0023 through 0025, wherein said population of nanoparticles has anaverage nanoparticle volume of from about 1000 nanometer cubed to about50,000 nanometer cubed, more preferably, from about 5000 nanometer cubedto about 50,000 nanometer cubed, most preferably from about 8000nanometer cubed to about 50,000 nanometer cubed of said nanoparticles.

Applicants disclose a three dimensional article according to Paragraphs0023 through 0026, wherein said matrix material is selected from thegroup consisting of a polymer, thermoplastics, thermosets, elastomersand mixtures thereof, preferably, said matrix material comprises apolymer, preferably said polymer is selected from the group consistingof Poly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO), poly(methylmethacrylate) (PMMA), poly(styrene) (PS) and mixtures thereof, morepreferably said polymer is selected from the group consisting ofPoly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO) and mixturesthereof, most preferably said polymer comprises Poly(vinyl alcohol)(PVA).

Applicants disclose a three dimensional article according to Paragraphs0023 through 0026, comprising an oxidant, said oxidant comprising acationic surfactants; preferably said oxidant is selected from the groupconsisting of halogenated surfactants and mixtures thereof, morepreferably said oxidant comprises an ammonium brominated surfactant,most preferably said oxidant comprises Hexadecyltrimethylammoniumbromide (CTAB), preferably said matrix comprises based on total threedimensional article weight, from about 0.0001% to about 50%, morepreferably, from about 0.01% to about 10%, most preferably from about 1%to about 5% of said oxidant.

Applicants disclose a three dimensional article according to Paragraphs0023 through 0026, comprising a reductant, said reductant being selectedfrom the group consisting of reducing agents, sugars, alcohols,carboxylic acids, aldehydes and mixtures thereof, preferably saidreductant is selected from the group consisting of alcohols andcarboxylic acids and mixtures thereof, more preferably said reductantcomprises an alcohol, most preferably said reductant comprises poly(vinyl alcohol), preferably said matrix comprises based on total threedimensional article weight, from about 10% to about 99.9999%, morepreferably, from about 25% to about 99.99%, most preferably from about95% to about 99.95% of said reductant. If the extra reducing agent needsto be introduced, the reducing agent comprises based on total threedimensional article weight, from about 0.0001% to about 50%, morepreferably, from about 0.01% to about 10%, most preferably from about 1%to about 5% of said reductant.

Process

Applicants disclose a process of reshaping a population ofnanoparticles, said process comprising

-   -   a) contacting said population of nanoparticles in a carrier,        said carrier having a viscosity of at least 3 cps, preferably        said carrier's viscosity is from about 3 cps to infinity, more        preferably from about 10,000 to infinity, most preferably from        about 30,000 to infinity, with an oxidant and a reductant,        preferably said contacting step comprising contacting said        population of nanoparticles with said oxidant, then contacting        said population of nanoparticles with said reductant    -   b) exposing said contacted population of nanoparticles to an        energy source for a sufficient period of time to provide said        population of nanoparticles with at least 0.01 Wcm⁻² or at least        1 Wcm⁻², preferably said contacted population of nanoparticles        are exposed to sufficient light to provide said population of        nanoparticles with from about 0.1 Wcm⁻² to about 13 Wcm⁻², more        preferably said contacted population of nanoparticles are        exposed to sufficient light to provide said population of        nanoparticles with from about 1 Wcm⁻² to about 13 Wcm-2, most        preferably said contacted population of nanoparticles are        exposed to sufficient light to provide said population of        nanoparticles with from about 10 Wcm⁻² to about 13 Wcm⁻².

Applicants disclose a process according to Paragraph 0030 wherein saidexposing said contacted population of nanoparticles to an energy sourcecomprises exposing said contacted population of nanoparticles to:

-   -   a) light having a wavelength from about 190 nanometers to about        2500 nanometers, preferably said light having a wavelength of        from about 200 nanometers to about 2000 nanometers, more        preferably said light having a wavelength of from about 350        nanometers to about 1500 nanometers, most preferably said light        having a wavelength of from about 400 nanometers to about 1200        nanometers, for at least one second, preferably from about 1        second to about 60 min, more preferably from about 5 sec to        about 30 min, most preferably from about 10 sec to about 5 min;        or    -   b) a heat source, preferably said heat source is selected from        an oven, hot plate and combinations thereof;        preferably exposing said contacted population of nanoparticles        to an energy source comprises exposing said contacted population        of nanoparticles to said light. Light is the preferred energy        source as light allows for a more controlled and faster        reshaping process.

Applicants disclose a process according to Paragraphs 0030 through 0031,wherein said carrier is a three dimensional article comprising saidreductant and said population of nanoparticles are coated with saidoxidant, said population of nanoparticles being dispersed within saidthree dimensional article.

Test Methods

Morphology Gradient Test

The morphology gradient of population of nanoparticles is measured viaplasmonic shift as provided in the test method titled ASTM E275-08 usinga CRAIC microspectrometer. A single sample is used to determine themorphology gradient of population of nanoparticles. The sample size isas required by the CRAIC microspectrometer instructions. Using the CRAICmicrospectrometer the longitudinal peak position and shortest peakposition as well as the distance between the two peaks isdetermined—peak positions are determined from extinction spectrum. Forpurposes of the present specification, the morphology gradient is thedifference between longitudinal peak position and shortest peak positiondivided by the distance between the two populations. The resultingmorphology gradient is expressed in units of nm/μm.

Weight Percent of Nanoparticles Test

Nanoparticle weight percent is determined by the mass of totalnanoparticles divided by total material mass. The mass of the totalnanoparticles is estimated using a UV-Vis-NIR spectrometer as specifiedbelow and the Beer-Lamberts equation.A _(L-LSPR) =ε·C _(AuNR) ·LWhere A is the optical density of the nanoparticle solution, a isextinction coefficient of the nanoparticles, L is the path length. Fromthis equation, the concentration of nanoparticles is estimated andconverted to the mass.

UV-Vis-NIR spectrometer Specification

-   -   Measure 175 to 3300 nm using a PbSmart NIR detector for extended        photometric range    -   WinUV software—modular software with power analysis and enhanced        transfer and report export capabilities    -   Variable slit widths (down to 0.01 nm) for optimum control over        data resolution    -   Maximum light throughput using Schwarzchild coupling optics for        higher accuracy at low transmission levels    -   Minimal noise and stray light using a floating aluminum casting        and double Littrow monochromator    -   Extended dynamic range by attenuating the reference beam more in        line with the sample absorbance.

Average Nanoparticle Volume Test

Average nanoparticle volume is determined by TEM image analysis whichmeasures the dimension (length and width) of nanoparticles. 500particles are measured from the respective sample and the average volumeof the 500 particles is considered the Average Nanoparticle Volume.

Viscosity Test

For purposes of the present application viscosity is determined by usingthe following method: (ref: ISSN 1392-2114 ULTRAGARSAS (ULTRASOUND),Vol. 66, No. 4, 2011)

EXAMPLES

The following example illustrates particular properties and advantagesof some of the embodiments of the present invention. Furthermore, theseare examples of reduction to practice of the present invention andconfirmation that the principles described in the present invention aretherefore valid but should not be construed as in any way limiting thescope of the invention.

Example 1: Process of Making and Reshaping a Population of Nanoparticlesand Making Three Dimensional Article Using Polyvinyl Alcohol

Materials: Hexadecyltrimethylammonium bromide (CTAB) was purchased fromGFS chemicals. Hexadecyltrimethylammonium chloride (CTAC) was purchasedfrom Aldrich. Benzyldimethylhexadecylammonium chloride (BDAC) waspurchased from TCI America. HAuCl4, AgNO3, sodium borohydride andL-ascorbic acid were purchased from Aldrich. Polyvinylalcohol (PVA,MW=89,000-98,000, 99+% hydrolyzed, Tg=80° C., 341584) and polyethyleneoxide (PEO, MW=35,000, Tg=65° C.) were purchased from Sigma-Aldrich.Thiol terminated polystyrene (PS-SH, MW=10,000) and bulk polystyrene(MW=35,000) were purchased from Polymer Source and Sigma-Aldrich,respectively.

Synthesis of AuNRs and fabrication of AuNR/polymer composites: The AuNRswere synthesized according to seed growth method modified for scale upproduction as in accordance with the method provided in Park, K.; Hsiao,M.-s.; Yi, Y.-J.; Izor, S.; Koerner, H.; Jawaid, A.; Vaia, R. A. HighlyConcentrated Seed-Mediated Synthesis of Monodispersed Gold Nanorods. ACSApplied Materials & Interfaces 2017. AuNR dimensions were determinedthrough both UV-Vis spectroscopy as well as TEM image analysis. As-madeAuNRs were purified from the growth solution via a series ofcentrifugation steps to remove unreacted reactants. The initial growthsolution was first centrifuged at 8500 RCF (relative centrifugal force)in a 50 mL tube for 30 minutes. The sedimented nanorods were thentransferred to a 2 mL centrifuge tube and subsequently spun at 9600 RCFfor 30 minutes. After centrifugation, the supernatant was removed andreplaced with a 25 mM CTAB/DI-H₂O solution. This washing step wasrepeated two times. The solution of AuNRs was then stored (aged) at roomtemperature and standard pressure for 3-6 additional days. For the PSgrafted AuNRs, a ligand exchange was done through solvent transferprocesses of CTAB coated AuNRs in DI-H₂O to PS-SH (10 mM) in toluene.Average nanoparticle volume of the is determined in accordance with thetest method of the present specification and is found to be 5340 nm3

To fabricate films, the AuNR stock solution was added to 2 mL solutionof 10 wt % PVA in H₂O (or 10 wt % PS in toluene for the PS-graftedAuNRs.) To vary the amount of CTAB in AuNR films, either additional CTABwas added to the solution before drop casting, or an additional washstep was implemented to remove excess CTAB. The amount of CTAB wasconfirmed through UV-Vis. The AuNRs-PVA/H₂O (or PS/toluene) solution washomogenously mixed through bath sonication, after which was left tosettle, in the case of any potential bubbles that formed in the solutionfrom sonication. After settling, the solution was drop cast on 2 in×2 inglass slides and spread evenly across the glass for controlled solutioncasting. After drop casting, the films were left to dry overnight. Theconcentration of AuNRs was determined using Beer-Lambert's Law wherefilm thickness was measured with a micrometer, optical density wasdetermined at the longitudinal surface plasmon resonance (L-LSPR) peakusing UV-Vis-NIR spectroscopy and extinction coefficient for NRs of agiven dimension was used from Park, K.; Biswas, S.; Kanel, S.; Nepal,D.; Vaia, R. A. Engineering the Optical Properties of Gold Nanorods:Independent Tuning of Surface Plasmon Energy, Extinction Coefficient,and Scattering Cross Section. The Journal of Physical Chemistry C 2014,118, 5918-5926. Films of aligned AuNRs were prepared by post-processthrough incremental stretching of the PVA composite at 90° C. (10° C.above Tg).

Thermal and photo-thermal processing of AuNRs/polymer nanocomposites:For thermal processing, films were placed in a conventional oven or on acalibrated gradient hot plate. For photo-thermal processing, a CRAIC XeArc Lamp was used as a light source (approximated power density 10W/cm², spot size ca. 1 mm diameter). Unless otherwise noted, the solidAuNR/PVA films were mounted on a conventional glass slide. The reportedoptical power densities were experimentally determined using a Thor Labsthermal power meter (model 5302C.) The bulk temperature of thephoto-thermal processed films was estimated by a calibrated IR camera(Model FLIR SC620)

Optical patterning: The color map (FIG. 4) for various combination ofexposure time and irradiation power was produced using broadband lightfrom the CRAIC at varying exposure times and power densities. The filmwas not mounted on glass. The printed thunderbird film (FIG. 5) wasacquired using a diode pumped solid state laser at 442 nm wavelengthwith a spot size of 100 μm, power density of 40 mW/cm² and irradiationtime of 500 ms. For the altimeter film (FIG. 6), similar specificationswere used, however two exposure times (750 ms and 1500 ms) were chosento reshape the rods to AR=2 and AR=1, respectively.

Morphology gradient is determined in accordance with the test method ofthe present specification and is found to be a longitudinal plasmonresonance of 0.01 eV mm⁻¹ (3 nm mm⁻¹). Weight percent of nanoparticlesis determined in accordance with the test method of the presentspecification and is found to be 0.3%

Example 2: Process of Making and Reshaping a Population of Nanoparticlesand Making Three Dimensional Article Using Poly (Carboxylate-Co-VinylAlcohol)

Example 1 was repeated except the PVA is replaced with Poly(carboxylate-co-vinyl alcohol) having approximately the same MW and Tgas the PVA used in Example 1. Approximately the same results as obtainedin Example 1 are obtained.

Example 3: Process of Making and Reshaping a Population of Nanoparticlesand Making Three Dimensional Article Using Acrylic Acid-Vinyl AlcoholGraft Copolymers

Example 1 was repeated except the PVA is replaced with Acrylicacid-vinyl alcohol graft copolymers having approximately the same MW andTg as the PVA used in Example 1. Approximately the same results asobtained in Example 1 are obtained.

Example 4: Process of Making and Reshaping a Population of Nanoparticlesand Making Three Dimensional Article Using Ethylene-Vinyl AlcoholCopolymers

Example 1 was repeated except the PVA is replaced with Ethylene-vinylalcohol copolymers having approximately the same MW and Tg as the PVAused in Example 1. Approximately the same results as obtained in Example1 are obtained.

Example 5: Process of Making and Reshaping a Population of Nanoparticlesand Making Three Dimensional Article Using Glycosylated Poly(VinylAlcohol)

Example 1 was repeated except the PVA is replaced with Glycosylatedpoly(vinyl alcohol) having approximately the same MW and Tg as the PVAused in Example 1. Approximately the same results as obtained in Example1 are obtained.

Every document cited herein, including any cross referenced or relatedpatent or application and any patent application or patent to which thisapplication claims priority or benefit thereof, is hereby incorporatedherein by reference in its entirety unless expressly excluded orotherwise limited. The citation of any document is not an admission thatit is prior art with respect to any invention disclosed or claimedherein or that it alone, or in any combination with any other referenceor references, teaches, suggests or discloses any such invention.Further, to the extent that any meaning or definition of a term in thisdocument conflicts with any meaning or definition of the same term in adocument incorporated by reference, the meaning or definition assignedto that term in this document shall govern.

While the present invention has been illustrated by a description of oneor more embodiments thereof and while these embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus andmethod, and illustrative examples shown and described. Accordingly,departures may be made from such details without departing from thescope of the general inventive concept.

What is claimed is:
 1. A process of reshaping a population ofnanoparticles, said process comprising a) contacting said population ofnanoparticles in a carrier, said carrier having a viscosity of at least3 cps, with an oxidant and a reductant; b) exposing said contactedpopulation of nanoparticles to an energy source for a sufficient periodof time to provide said population of nanoparticles with from about 0.1Wcm⁻² to about 13 Wcm⁻².
 2. The process according to claim 1 whereinsaid exposing said contacted population of nanoparticles to an energysource comprises exposing said contacted population of nanoparticles to:a) light having a wavelength from about 190 nanometers to about 2500nanometers, for at least one second; or b) a heat source.
 3. The processaccording to any claim 1, wherein said carrier is a three dimensionalarticle comprising said reductant and said population of nanoparticlesare coated with said oxidant, said population of nanoparticles beingdispersed within said three dimensional article.